The Flanders NaturalAire Electrostatic Series 50855.011520 Washable Air Filter is a MERV 10 rated washable air filter which uses its electrostatically charged media to capture airborne contaminants. This 15" x 20" x 1" filter provides superior filtration against common household contaminants such as dust mites, mold, pet dander, and pollen. NaturalAire Electrostatic Series filters can be washed once and month and are good for up to 5 years, granting an economic solution to your homes HVAC system.